Aluminoxanes are of commercial importance as components used in forming polymerization and oligomerization catalysts. They are formed by controlled hydrolysis of aluminum alkyls such as trimethylaluminum. While the hydrolysis can be effected by use of hydrated crystalline salts such as the pentahydrate of copper sulfate or the like, this approach can lead to the presence in the product of small amounts of metal residues which can act as catalyst poisons. Thus the use of water itself to effect controlled hydrolysis of the aluminum alkyl in a hydrocarbon medium has proven to be the preferred general approach.
Over the years considerable effort has been devoted to processes for conducting such controlled hydrolysis using water as the hydrolytic reagent. For example, Vandenberg, U.S. Pat. No. 3,219,591 reported the catalytic activity of compounds formed by the reaction of trialkylaluminum with limited amounts of water in the polymerization of epichlorohydrin and other oxiranes. Shortly thereafter, Manyik, et al. U.S. Pat. No. 3,242,099 reported the use of aluminoxanes, made by reacting 0.85-1.05 moles of water with hydrocarbylaluminum compounds such as triisobutylaluminum, as co-catalysts with certain transition metal compounds in the polymerization of mono-unsaturated alpha-olefins; e.g. ethylene and propylene. Isobutylaluminoxane was also made by adding an equal mole quantity of water to a heptane solution of triisobutylaluminum.
Manyik, et al. U.S. Pat. No. 3,300,458 describe preparing alkylaluminoxane by passing a hydrocarbon through water to form a wet hydrocarbon and mixing the wet hydrocarbon and an alkyl aluminum/hydrocarbon solution in a conduit. Manyik, et al. in Journal of Catalysis Volume 47 published in 1977, at pages 197-209, refer to studies with catalysts formed from certain chromium compounds and partially hydrolyzed triisobutylaluminum.
Schoenthal, et al. U.S. Pat. No. 4,730,071 shows the preparation of methylaluminoxane by dispersing water in toluene using an ultrasonic bath to cause the dispersion and then adding a toluene solution of trimethylalaminum to the dispersion. Schoenthal, et al. U.S. Pat. No. 4,730,072 is similar except it uses a high speed, high shear-inducing impeller to form the water dispersion.
Edwards, et al. U.S. Pat. No. 4,772,736 describes an aluminoxane preparation process in which water is introduced below the surface of a solution of hydrocarbylaluminum adjacent to a stirrer which serves to immediately disperse the water in the hydrocarbon solution.
Bottelberghe U.S. Pat. No. 4,908,463 describes an aluminoxane preparation process in which a static mixer is used to disperse water in a solvents and then impinges the water dispersion with a hydrocarbylaluminum solution in a T-shaped reactor. The solution is then removed to a finished reaction vessel which is stirred and can have a cooling means such as a heat-exchanger in an external pump-around loop.
Bottelberghe U.S. Pat. No. 4,924,018 describes formation of aluminoxanes by feeding a hydrocarbon solution of aluminum alkyl to a reaction zone, feeding an emulsion of 0.5-10 weight percent water in an inert solvent to the reaction zone, the ratio of moles of water to aluminum atoms being about 0.4-1:1, and removing reaction mixture from the reaction zone to maintain a constant liquid level therein. The feeds are controlled so that the average residence time in the reaction zone is no more than about one hour.
Smith, Jr., et al. U.S. Pat. No. 4,937,363 discloses forming aluminoxanes by forming in a column a thin falling film of a solution of aluminum alkyl in an inert solvent while passing an upward countercurrent flow of wet inert gas through the column.
Davis U.S. Pat. No. 4,968,827 teaches introducing water into the free space above the surface of a cold (-80.degree. C. up to -10.degree. C.) solution of hydrocarbylaluminum compound in a liquid hydrocarbon which is being intensively agitated.
Deavenport, et al. U.S. Pat. No. 5,041,585 and 5,206,401 teach preparation of aluminoxanes by contacting an organic solvent containing trialkylaluminum with atomized water. Preformed aluminoxane can be included in the solution as reaction moderator.
Becker et al. U.S. Pat. No. 5,403,942 and Graefe et al. U.S. Pat. No. 5,427,992 describe batch processes for preparing aluminoxanes by injecting water into trialkylaluminum solutions using respectively, a jet loop reactor and a rotor/stator machine to mix the water and trialkylaluminum.
U.S. Pat. No. 4,960,878; 5,041,584 and 5,086,024 also describe processes in which water and certain organoaluminum compounds are caused to interact.
Despite all such intensive study and research, a need exists for practical, commercially-feasible process technology capable of producing concentrated aluminoxane solutions with no significant yield losses, especially where such technology can be applied both to batch and to continuous modes of operation.
This invention is deemed to fulfill the foregoing need in a highly efficient manner.